Pure compounds

Wichterle, I., and J. Linek "Antoine Vapor Pressure Constants of Pure Compounds," Academia, Prague, 1971. 

Presents Antoine vapor-pressure constants for pure compounds for two pressure ranges. 

Knowledge of physical properties of fluids is essential to the process engineer because it enables him to specify, size or verify the operation of equipment in a production unit. The objective of this chapter is to present a collection of methods used in the calculation of physical properties of mixtures encountered in the petroleum industry, different kinds of hydrocarbon components, and some pure compounds. 

The factor enabling interpolation of reduced properties of a pure compound or mixture between two reduced properties calculated on two reference fluids merits attention in order to understand its meaning. 

At a given temperature and pressure, a pure compound can exist in one, two or three states. The compound exists at three different states at the triple point and at two different states along the curves of vaporization, freezing and sublimation. Refer to Figure 4.6. 

This database provides thermophysical property data (phase equilibrium data, critical data, transport properties, surface tensions, electrolyte data) for about 21 000 pure compounds and 101 000 mixtures. DETHERM, with its 4.2 million data sets, is produced by Dechema, FIZ Chcmic (Berlin, Germany) and DDBST GmhH (Oldenburg. Germany). Definitions of the more than SOO properties available in the database can be found in NUMERIGUIDE (sec Section 5.18). 

A further advancement in organic synthesis was the accomplishment of multi-step syntheses comprising 20 and more steps and the synthesis of rather unstable organic compounds. It was now feasible to do an experiment on a milligram scale and to separate and identify products from by-products in order to analyze them separately. The application of selective reagents or reaction conditions allowed the synthesis of enantiomerically or diastereomerically pure compounds. 

II). Pure Compounds decomposing slightly before melting. Lactose. Melts slowly between about 205 and 215 , with preliminary darkening and subsequent decomposition. 

The breaking up of azeotropic mixtures. The behaviour of constant boiling point mixtures simulates that of a pure compound, because the composition of the liquid phase is identical with that of the vapour phase. The composition, however, depends upon the pressure at which the distillation is conducted and also rarely corresponds to stoichiometric proportions. The methods adopted in practice will of necessity depend upon the nature of the components of the binary azeotropic mixture, and include —... 

The mono-methyl, ethyl and n-butyl ethers are inexpensive commercial products and are known as methyl carbitol, carbitol and butyl carbitol respectively. They are all completely miscible with water and are purified as already described for the cellosolves (10). The boiling points of the pure compounds are —... 

Methyl acetate. An anhydrous product of 99 per cent, purity (b.p. 56-5-57°) i.s available coniniercially this is comparatively cheap so that purification of inferior products is not worth while. It is appreciably soluble in water (ca. 24 per cent, at 20°). The pure compound has b.p. 57°/760 mm. 

The analytical reagent grade is suitable for most purposes. The commercial substance may be purifled by shaking for 3 hours with three portions of potassium permanganate solution (5 g. per litre), twice for 6 hours with mercury, and Anally with a solution of mercuric sulphate (2-5 g. per litre). It is then dried over anhydrous calcium chloride, and fractionated from a water bath at 55-65°. The pure compound boils at 46-5°/760 mm. 

Nitro-n-hexane. Use 41 g. of dry silver nitrite, 51 g. of n-hexyl iodide (35-5 ml.) and 100 ml. of sodium dried ether. Reflux on a water bath for 8 hours decant the ethereal solution and wash the sohd well with sodium dried ether. Distil the residue, after the removal of the ether from the combined extracts, from 5 g. of dry silver nitrite, and collect the fraction of b.p. 190-192° (13 g.) as 1-nitro -hexane. The pure compound is obtained by distilling under diminished pressure b.p. 81 6°/15 mm. 

Method 1. Place in a test-tube or small flask 1-3 g. of glycerol and 30 ml. of 10 per cent, sodium hydroxide solution add gradually, with simultaneous shaking, 1-2 g. of benzoyl chloride. Stopper the vessel, shake for several minutes and allow to stand. Decant the solution from the pasty solid and wash the latter with cold water by decantation. Recrystallise the solid tribenzoate from dilute rectified (or methylated) spirit or from light petroleum, b.p. 40-60° the pure compound has m.p. 76°. 

Dissolve 5 g. of finely-powdered diazoaminobenzene (Section IV,81) in 12-15 g. of aniline in a small flask and add 2-5 g. of finely-powdered aniline hydrochloride (1). Warm the mixture, with frequent shaking, on a water bath at 40-45° for 1 hour. Allow the reaction mixture to stand for 30 minutes. Then add 15 ml. of glacial acetic acid diluted with an equal volume of water stir or shake the mixture in order to remove the excess of anihne in the form of its soluble acetate. Allow the mixture to stand, with frequent shaking, for 15 minutes filter the amino-azobenzene at the pump, wash with a little water, and dry upon filter paper Recrystallise the crude p-amino-azobenzene (3-5 g. m.p. 120°) from 15-20 ml. of carbon tetrachloride to obtain the pure compound, m.p. 125°. Alternatively, the compound may be recrystaUised from dilute alcohol, to which a few drops of concentrated ammonia solution have been added. 

Ethyl cinnamate may also be prepared by the esterification of cinnamic acid. The pure compound boils at 127°/6 mm. 

Mix intimately in a mortar 100 g. of sodium laevulinate, 250 g. of phosphorus sulphide (1) and 50 g. of clean dry sand. Place the mixture in a flask fitted with a condenser for distillation and a receiver (2). Heat the flask with a free flame until the reaction commences, and then remove the flame. When the reaction subsides, continue the heating until distillation ceases. Wash the distillate with 10 per cent, sodium hydroxide solution to remove acidic by-products and steam distil. Separate the crude 2-methyltliiophene from the steam distillate, dry over anhydrous calcium sulphate, and distil from a little sodium. Collect the pure compound at 113° the yield is 30 g. 

The reaction between phthalonitrUe and copper also takes place readily in feoihng quinoline or a-methyhiaphthalene the pigment is precipitated as fast as it is formed as a crystalline product. It is separated from the excess of copper by shaking with alcohol, when the metal sinks and the pigment, which remains in suspension, can be poured off the process may be repeated to give the pure compound. 

Dimethylaminomethylindole (gramine). Cool 42 5 ml. of aqueous methylamine solution (5 2N ca. 25 per cent, w/v) contained in an 100 ml. flask in an ice bath, add 30 g. of cold acetic acid, followed by 17 -2 g. of cold, 37 per cent, aqueous formaldehyde solution. Pour the solution on to 23 -4 g. of indole use 10 ml. of water to rinse out the flask. Allow the mixture to warm up to room temperature, with occasional shaking as the indole dissolves. Keep the solution at 30-40° overnight and then pour it, with vigorous stirring, into a solution of 40 g. of potassium hydroxide in 300 ml. of water crystals separate. Cool in an ice bath for 2 hours, collect the crystalline solid by suction flltration, wash with three 50 ml. portions of cold water, and dry to constant weight at 50°. The yield of gramine is 34 g. this is quite suitable for conversion into 3-indoleacetic acid. The pure compound may be obtained by recrystaUisation from acetone-hexane m.p. 133-134°. 

Clearly, there is a need for techniques which provide access to enantiomerically pure compounds. There are a number of methods by which this goal can be achieved . One can start from naturally occurring enantiomerically pure compounds (the chiral pool). Alternatively, racemic mixtures can be separated via kinetic resolutions or via conversion into diastereomers which can be separated by crystallisation. Finally, enantiomerically pure compounds can be obtained through asymmetric synthesis. One possibility is the use of chiral auxiliaries derived from the chiral pool. The most elegant metliod, however, is enantioselective catalysis. In this method only a catalytic quantity of enantiomerically pure material suffices to convert achiral starting materials into, ideally, enantiomerically pure products. This approach has found application in a large number of organic... 

NMR). Distillation through a 10-cm Vigreux column gave the pure compound, b.p. 

Studies aimed at characterizing the mechanisms of electrode reactions often make use of coulometry for determining the number of electrons involved in the reaction. To make such measurements a known amount of a pure compound is subject to a controlled-potential electrolysis. The coulombs of charge needed to complete the electrolysis are used to determine the value of n using Faraday s law (equation 11.23). 

In situations where conserved internal markers caimot be used, such as in spills of essentially pure compounds, the evidence for enhanced biodegradation may have to be more indirect. Oxygen consumption, increases in microbial activity or population, and carbon dioxide evolution have all been used with success. 

Chiral synthetic polymer phases can be classified into three types. In one type, a polymer matrix is formed in the presence of an optically pure compound to moleculady imprint the polymer matrix (Fig. 10) (107,108). Subsequent to the polymerisation, the chiral template is removed, leaving the polymer matrix... 

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